Seven Sisters (Messier object 45 or M45), is an open star cluster containing middle-aged hot B-type stars located in the constellation of Taurus.  The most famous star cluster on the sky, the bright stars of the Pleiades can be seen without binoculars from even the depths of a light-polluted city.

Under ideal observing conditions, some hint of nebulosity may be seen around the cluster, and this shows up in long-exposure photographs. It is areflection nebula, caused by dust reflecting the blue light of the hot, young stars. It was formerly thought that the dust was left over from the formation of the cluster, but at the age of about 100 million years generally accepted for the cluster, almost all the dust originally present would have been dispersed by radiation pressure. Instead, it seems that the cluster is simply passing through a particularly dusty region of the interstellar medium. Studies show that the dust responsible for the nebulosity is not uniformly distributed, but is concentrated mainly in two layers along the line of sight to the cluster. These layers may have been formed by deceleration due to radiation pressure as the dust has moved towards the stars.

Imaging telescopes or lenses: Takahashi FSQ Fluorite
Imaging cameras: SBIG STL-11000M
Mounts: Paramount GT-1100S
Dates: Oct. 2, 2013
Locations: Mayhill
Frames:
4×300″ bin 1×1
RGB filters: 3×300″ bin 1×1
Integration: 0.6 hours

Autor: Giulio Ercolani

AstroPhotography of the day by SPONLI

28 January 2014

We select the best works of amateur astrophotographers with details of equipment, shooting processing etc.